| 摘要 |
PURPOSE:To prevent a DC servo motor to be controlled from running away by immediately turning OFF a power source of a drive circuit when a speed feedback signal is not abnormally fed back in case that the voltage as a speed command signal at the time of energizing a power source is extremely low. CONSTITUTION:The first comparator 11 detects the fact that the absolute value of a speed command signal e1 is lower then the prescribed value. The second comparator 12 detects the fact that a pulse width designation signal t1 based on a negative feedback signal becomes higher than the prescribed value. When signals are simultaneously outputted from the first and second comparators 11, 12, a processor 13 operates to shut off the power source of a drive circuit 6. Since thus constructed, a DC motor can be, when the feedback circuit is opened or shortcircuited, rapidly stopped. |
